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5.Magnetism and Matter
easy
Two points $A$ and $B$ are situated at a distance $x$ and $2x$ respectively from the nearer pole of a magnet $2\,cm$ long. The ratio of magnetic field at $A$ and $B$ is
A
$4 : 1$ exactly
B
$4 : 1$ approximately
C
$8 : 1$ approximately
D
$1 : 1$ approximately
Solution
Taking distances from the centre of the magnet,
$\frac{{{B_1}}}{{{B_2}}} = {\left( {\frac{{{x_2}}}{{{x_1}}}} \right)^3} = {\left( {\frac{{2x + 1}}{{x + 1}}} \right)^3} = 8:1$ , approximaetly.
Standard 12
Physics
